There has been developed a hybrid electric rotary excavator of which a rotary body is driven by an electric motor while a work machine and a carrier thereof are driven by a hydraulic actuator (see, for example, Patent Document 1).
In such an electric rotary excavator, the rotary body is rotated by the electric motor. Even when the rotary body is rotated at the same time of an elevation of a boom or an arm which is hydraulically driven, the movement of the rotary body is not affected by the elevation of the boom or the arm. Hence, the energy efficiency is better as compared to a case in which the rotary body is also driven hydraulically, since energy loss through a control valve and the like can be reduced.
[Patent Document 1] JP2001-11897A